To not let things get to you, and allow yourself not to be bothered or annoyed by actions or the current situation you may be in or by what other are doing to manipulate you into bitterness. When everything is building up. i.e. The saying when it rains it pours seems to make sense in describing life at times and acting like a duck is better, because ducks do not run and hide when it rains, they do not try to cover themselves up and avoid it, they do not attack the rain or try fighting it off they simply endure it with pride and dignity like it was not even there in fact they seem to enjoy it while it lasts, and above all do not seem to be bothered by the rain. Hence acting like a duck or to act like a duck is better than retaliating and making the situation worse or make everyone think its better to attack and fight rather than be dignified and work it out.
My boss was a jerk and was ripping every one of his customers off, I said something about it, and he made my life difficult by demoting me and threatened to fire me next. I went home the wife through a fit saying we owe more than we can afford and are getting evicted, my kids crying because she is screaming, the landlord is calling harassing me over raising the rent. The car needs new tires, and it barely runs and I just act like a duck and try to work it all out somehow, because its better to work it out than add to the problem with retaliation, anger and uncontrollable vulgarities.